The percentage of infertile couples around the world is increasing every year. Specialists find various reasons, and one of them is environmental pollution. In fact, we do not think about the global nature of this problem, although according to the WHO, various kinds of chemicals provoke 25% of all diseases on the globe and more than a third of pathologies in children. Moreover, the growing number of cancerous diseases makes scientists believe that chemicals also cause cancer.
How exactly do chemicals affect our reproductive health? Do they cause cancer? Let’s find this out.
How chemicals affect human health
The environment can negatively affect the quality of the ejaculation and functioning of testicles due to impaired synthesis of steroid hormones, as well as by direct damage to the tissues of the reproductive organs. The effect, though, depends on the type of chemical.
Heavy metals (cadmium, lead, mercury, etc.)
Heavy metals have long been used in manufacturing. Cadmium is used as a component of alloys, as well as in the production of batteries, anti-corrosion coatings and coloring materials. Lead is indispensable in metallurgy, in the manufacture of paints, insecticides, explosives. Mercury is used in the manufacture of electronics, in instrument making and metallurgy.
All this must be taken into account when collecting an anamnesis of patients in reproduction clinics. Heavy metals can accumulate in the reproductive tissues of both men and women. The mechanism of a negative effect on fertility lies in the induction of oxidative stress, which provokes DNA damage.
From school, we know about mercury toxicity. The FDA (U.S. Food and Drug Administration) recommends restricting the use of certain types of fish as the main source of mercury in foods for pregnant, lactating mothers and children. The list of dangerous seafood included Chilean sea bass, shark, mackerel, almost all types of tuna, rolls and sushi from the supermarket. According to a multicenter study in North America, the level of mercury found in the hair of infertility patients correlated with the amount of fish consumed. There was no effect on the level of sex hormones in IVF cycles, as well as embryological parameters and the success of treatment of these patients.
In a similar study involving infertile men, increased levels of mercury, manganese, and nickel were associated with increased sperm DNA fragmentation. In this study, urine samples were analyzed, although hair was able to accumulate mercury for a longer time.
In women with infertility of unknown origin, the influence of heavy metals on endometrial receptivity is assumed. A study by Tanrikut E. found cadmium and lead in an endometrial biopsy. Cadmium was detected in 91% of women with infertility of unknown origin compared with 34% of fertile patients. Lead was detected in 15% of infertile patients and in 3% of fertile patients. Scientists suggest that the physiological role of cadmium in infertility of unknown origin is the adverse effect on embryo implantation. Cadmium is also considered the culprit in the formation of uterine fibroids, which in turn is able to accumulate heavy metals, which forms a vicious circle.
Prescribing non-specific antioxidant therapy (vitamins) to both men and women 3 months before the IVF protocol improves treatment outcomes. However, to date, there is no evidence base for prescribing detoxification therapy to patients with infertility.
It is used in the production of products made of polycarbonate plastic and epoxy resins (plastic dishes, medical equipment). Despite the short half-life (6–24 hours), bisphenol A can accumulate in various reproductive tissues — follicular fluid, placenta, even in breast milk.
In infertility, an elevated level of bisphenol A is observed compared with fertile women. In IVF programs, the level of this toxicant in the blood of patients negatively affected the level of serum estradiol and, accordingly, the frequency of fertilization and the quality of the embryos.
Bisphenol A negatively affects male fertility, causing pathozoospermia and a decrease in steroid hormones. It directly damages spermatogenic epithelium. Given these facts, the use of plastic utensils should become taboo.
The negative effect of phthalates, which are used in the manufacture of plastic, has been studied for over 30 years. They negatively affect the quality of the ejaculate and the level of sperm DNA fragmentation, increases the risk of giving birth to children with congenital anomalies. In IVF programs, the levels of phthalates in the body of men correlate with deteriorating embryo quality and pregnancy rates. Scientists associate the negative impact of phthalates with the depletion of the ovarian reserve in women.
It has long been used for the conservation of biomaterials, therefore, medical workers and laboratory workers can theoretically be exposed to negative effects. Formaldehyde is known for its cytotoxic properties. It violates spermatogenesis — the concentration, motility and morphology of sperm.
It is released into the environment during the combustion of various types of combustible materials. The source of the toxicant for humans is ambient air, tobacco smoke, heating and road transport.
Benzpyrene is an endocrine disruptor (Endocrine disruptors). According to Canadian researchers, the concentration of benzpyrene in follicular fluid is associated with negative IVF attempts.
The source of benzpyrene is tobacco smoke. Smoking, both active and passive, it is rational to exclude at the stage of pregravid preparation for both women and men. Male smoking provokes fragmentation of sperm and shortening the length of telomeres in semen.
Raw materials for paints and adhesives, rubbers, solvents. Styrene has a general toxic, mutagenic and carcinogenic effect. Dangers are workers in the chemical and wood processing industries. According to Italian researchers, men employed in chemical plants had elevated levels of DNA fragmentation and aneuploidy in sperm.
Chemicals and cancer: what’s the connection?
Scientists have not yet fully decided how best to classify the cancerogens (cancer-causing chemical): they are divided either into radioactive (this group includes all types of hazardous radiation) and non-radioactive, then into genetic and environmental ones. The latter include lifestyle factors — smoking, alcoholism, unhealthy diet, low level of physical activity, and exposure to sunlight or viruses, and work in hazardous industries, and the use of certain medications like chemotherapy drugs. By and large, it does not matter how to classify carcinogens — it is important what this can give in practice. Indeed, if certain therapy, even bearing the risk of carcinogenesis, can sometimes not be abandoned, then the effects of other factors can be minimized (for example, protecting the skin from the sun or stopping smoking).
Carcinogens affect DNA, causing dangerous changes — but the latter do not necessarily lead to the formation of a tumor, they only increase the likelihood that the reproduction of abnormal cells will reach a level at which the immune system cannot cope with. A recent study found that two-thirds of the genetic mutations that lead to cancer are errors that occur spontaneously when copying DNA, and only the remaining third occurs under the influence of environmental carcinogens.
How to protect yourself from the negative impact of the external environment?
Healthy nutrition, adequate physical activity, rejection of bad habits, change of job — once you change your lifestyle to the better you will feel the difference. All we can do is reduce the contact with chemicals in all possible ways and give preference to natural food, clothes, and furniture. It might seem to bring minor changes, but your efforts will pay off in a long term!